Well control is an important aspect of oil and gas exploration. When drilling a well, for example, in oil and gas exploration applications, safety devices must be put in place to prevent injury to personnel and damage to equipment resulting from unexpected events associated with the drilling activities.
Drilling wells in oil and gas exploration involves penetrating a variety of subsurface geologic structures, or “layers.” Occasionally, a wellbore will penetrate a layer having a formation pressure substantially higher than the pressure maintained in the wellbore. When this occurs, the well is said to have “taken a kick.” The pressure increase associated with the kick is generally produced by an influx of formation fluids (which may be a liquid, a gas, or a combination thereof) into the wellbore. The relatively high pressure kick tends to propagate from a point of entry in the wellbore uphole (from a high pressure region to a low pressure region). If the kick is allowed to reach the surface, drilling fluid, well tools, and other drilling structures may be blown out of the wellbore. These “blowouts” often result in catastrophic destruction of the drilling equipment (including, for example, the drilling rig) and substantial injury or death of rig personnel.
Because of the risk of blowouts, blowout preventers (“BOP”) are typically installed at the surface or on the sea floor in deep water drilling arrangements to effectively seal a wellbore until active measures can be taken to control the kick. Blowout preventers may be activated so that kicks may be adequately controlled and circulated out of the system.
Just as a kick will propagate up the well, it may also enter the drill string and propagate through the inside of the drill string. To control a kick inside the drill string, a drill string internal blowout preventer (“IBOP”), sometimes called a “kelly valve” or a “kelly cock,” is used to seal off the drill string until measures can be taken to control the kick. (An IBOP is sometimes called a “kelly valve” because, on older-style rigs, the IBOP was typically located near the “kelly,” which is a non-circular part of the drill string that is used to impart rotary motion to the drill string.)
An IBOP is typically a ball valve or other type of valve that is connected in line with the drills string. It can be closed to isolate the kick inside the drill string. Because an IBOP and its associated actuator is connected in line with the drill string, it will rotate with the drill string during drilling operations.
Typically, IBOP's are pneumatically powered. The air source, typically a pressurized cylinder, is generally stationary. Thus, the challenge is to get the air power from the stationary source to the rotating IBOP actuator. It is noted that often drilling is stopped before the IBOP is actuated, but for safety reasons, the IBOP must be connected to an air supply at all times during drilling operations.
Prior art IBOP actuators have included a rotating section and a non-rotating section. Generally, the air source is routed into the non-rotating section, which is coupled to the rotation portion of the actuator by various types of seals, bearings, and air passageways. The air passes into the rotating portion of the actuator where it powers the actuator to close the IBOP.